Various physiologic signals are often recorded and analyzed. These signals may included digestive pH, various digestive motility and pressure signal, EEG and EMG, to list only a few.
Typically, physicians require the concurrent recording a variety of physiologic signals. For example, gastric pH is often collected at the same time as pressure. Through the concurrent collection of various parameters the physician may better understand the patient's condition.
Ambulatory recording and recorders are widely used to collect such data. Such devices include the Digitrapper Mk III.TM. ambulatory recorder from Synectics Medical AB, the GastroScan II.TM. from Medical Instruments Corporation, and the SuperLogger.TM. from Sandhill Scientific. These types of devices make it possible for patients to remain at home, or at the least be ambulant in a hospital setting while physiological data is recorded. Typically the devices comprise a lightweight recorder in which the desired physiological data signals are temporarily stored and later downloaded for future analysis.
Many types of physiological data may be recorded, including ECG (Electrocardiogram), EEG (Electroencephalogram) or pH and pressure (Motility) in the gastrointestinal tract. Preferably such a recorder should be able to record among a programmable number of channels at a variety of programmable frequencies, while still being small and rugged enough to be used as an ambulatory device.
Such recorders, because they must be ambulatory, are battery powered. Thus an ambulatory medical recorder must minimize energy usage while performing almost constant sampling across a variable number of channels at one or more frequencies. Besides minimizing energy usage, such recorders, however, must also offer robust functionality, i.e., be easy to operate, while also being flexible. Moreover, another crucial requirement is that such recorders be dependable, accurate and reliable.
One approach to construct a recorder offering flexible operation, ease of use, as well as a simple but powerful graphical user interface all while providing dependable, accurate and reliable data sampling and recording is through the use of two processors. This approach may include the use of processor having differing architectures. For example, first processor may be a real time processor ("RTP") which handles the sampling function, while the second processor may be a non real time processor ("NRTP") which handles the operating system function.
Among the problems with a data recorder using two processors is that of communication between the processors. Although this may be a problem regardless of the processors selected, in the situation where the first processor is a RTP and the second processor is a NRTP, the problem is especially acute. In particular, the RTP runs a real time single task software; while the NRTP runs a non-real time multitasking operating system and application with priorities. Thus, communication with the RTP could be started by several tasks within the NRTP at the same time. Ultimately this may lead to confusion in the recorder and ultimately lead to a system failure and/or data loss. While various approaches to coordinating the transfer of data between such processors may be used, there exists a need to provide a reliable but simple method of restarting communication should there be a failure.